1. Field of the Invention
The present invention relates to an acousto-electronic transducer especially adapted for use as an extremely small type, and more particularly, to an acousto-electronic transducer including an oscillator of quartz specially arranged so as to utilize its superior frequency characteristic.
2. Description of the Prior Art
In principle, the conventional microphones can be classified into a carbon type, an electro-magnetic type, and a dynamic type. In addition, there is another called a crystal type in which a substance having piezoelectric properties, such as Rochelle salt, is employed, and more recently there is a further type called a condenser type in which changes in electric capacity are utilized.
However, regardless of the common knowledge that quartz has superior electrical and acoustic properties it has not been employed for a microphone, because of its limited production and the resulting high price. The price is particularly so high that it is generally accepted as a jewery. In addition, when quartz is used for frequency control a thin plate must be appropriately cut from quartz crystals, which means that a usable portion of quartz is small, and an oscillator of quartz will become very expensive.
The known quartz oscillators have been used only for generating high frequency, but its resonance frequency is outside the audiofrequency domain.
Recently, however, the technology of man-made quartz has made remarkable progress, and the price has been reduced because of its mass-production. In addition, by virtue of the development of a tuning fork oscillator of quartz its resonance frequency has reached the supersonic wave domain, which is close to the audiofrequency domain. In particular, the development of crystal-controlled watches has paved the way to the low-priced mass-production of tiny tuning fork oscillators of quartz whose resonance frequency is for example 32.76 kHZ.
The present invention is directed to utilize the superior qualities of quartz as an acousto material, and has for its object to provide a small-size acousto-transducer with high articulation and fidelity and with high stability against any changes in temperature, humidity and pressure.